经济学人123:生态学里应用上了化学技术

 　　Science and Technology Animal behaviour Drip-feeding

　　科技 动物行为 滴定进食

　　Ecology raids the techniques of chemistry

　　生态学里应用上了化学技术。

　　BIOLOGISTS are sometimes accused of physics envy—and there is truth in this accusation¹. The essential fuzziness of biological systems can never be captured by the precise, mathematically based experiments of something like the Large Hadron Collider. Between physics and biology on the spectrum² of fuzziness, though, lies chemistry. And a group of researchers led by Carolyn Nersesian of the University of Sydney has just borrowed one of chemistry's most elegant techniques, titration, to answer a pressing ecological³ question: how do animals choose where to feed?

　　生物学家们常常被认为非常嫉妒研究物理学的人（事实上确实如此）。他们永远不可能通过像大型强子加速碰撞那样精确、量化的实验来揭示生物学里的一些关键性的奥秘。但是在这种奥秘的"两极"——物理学和生物学之间还有化学。最近由悉尼大学的卡洛琳·涅尔谢相带领的一组研究人员借用化学里一种非常精妙的技术——滴定法来解决一个迫待回答的问题：动物们如何选择觅食场所。

　　Titration, to remind those who dozed⁴ through their chemistry lessons, is a way of working out the concentration of a substance in a solution. A reagent of known concentration is dripped (or titrated, to use the term of art) into the unknown solution in the presence of an appropriate indicator⁵ molecule⁶ (for example litmus, in the case of a reaction between an acid and an alkali). When the tipping point comes, and all of the unknown reagent has reacted, the solution changes colour. The unknown concentration can then be calculated from the amount of known reagent used.

　　滴定法（为了给那些在化学课上打过瞌睡的同学们提个醒）是一种计算溶质在溶液中的浓度的方法。在某种特定的指示分子的参与下（例如，酸溶液和碱溶液的反应中我们使用石蕊指示剂），将一种已知浓度的溶液滴到（专业术语叫滴定）未知溶液中。当滴定终点到来时，所有的未知溶液全都完成了化学反应，溶液的颜色就会发生变化。然后未知溶液的浓度就可以通过被消耗掉的已知溶液的体积计算出来。

　　In Dr Nersesian's titration the litmus was a species called the brushtail possum. The two reagents were predators⁷ and poisons. In the wild, possums feed mainly on eucalyptus⁸ trees. Feeding in trees this way also keeps them safe from ground-based predators, such as foxes. They frequently have to shift from tree to tree in search of non-poisonous leaves, though, because a tree that is being browsed⁹ starts manufacturing toxins¹⁰. Dr Nersesian reasoned that there is probably a measurable point at which a plant becomes so toxic¹¹ that possums prefer to take their chances with the predators on the ground—and she realised this was a perfect opportunity to do an ecological titration.

　　涅尔谢相博士的滴定实验中的"石蕊指示剂"是一种叫帚尾袋貂的动物。那两种溶液是"猎食者"和"有毒物"。在野生环境下，袋貂主要以桉树叶为食。生活在树上也能让它们安全地远离地面上的那些猎食者——例如狐狸。但是他们还得经常从一棵树上换到另一棵树上去寻找那些没有毒的叶子。因为一颗树如果被它们吃久了就会自动分泌毒素。涅尔谢相博士认为可能当植物中的毒素达到一个量值的时候，袋貂会选择冒着被猎食的风险（途经地面换一棵树觅食），然后她就意识到这是一个应用生态滴定法绝好的机会。

　　As she reports in the Journal of Animal Ecology, she attempted to imitate the distinction between trees and ground by giving eight possums the opportunity to feed in either of two enclosures. In one, cover was created with eucalyptus branches and light levels were kept low, mimicking¹² an arboreal¹³ habitat. Here, the food was sometimes spiked¹⁴ with cineole—a poison often found in eucalyptus leaves. In the other enclosure, the food was always untarnished. However, no cover was provided and fox scent¹⁵, in the form of faeces and urine, was scattered¹⁶ liberally around, mimicking conditions on the ground.

　　她发表在动物生态学报上报告中写道：她通过给8只袋貂两种桉树来选择觅食来模拟树上和地面的区别。一棵桉树上，有特意放置的桉树枝来遮挡，光照强度也很低，模拟出适合树栖动物习性的环境。但是，这种树上的叶子有时含有桉树脑——桉树叶中常见的毒素。另一棵桉树上，叶子总是无毒的，但是，没有树枝的遮挡。而且通过将一些狐狸的"踪迹"，例如狐狸的脸谱尿液随意四散在周围，来模拟地面环境。

　　To start with, when the level of cineole was low, possums preferred the first enclosure. But as the drip of the titration went up, from 0% to 1% to 2% to 5% and ultimately to 10% of the food being cineole, their behaviour changed. It was not quite the sudden shift from litmus red to blue of an acid being neutralised by an alkali, but it was not far off.

　　开始桉树脑的浓度很低，袋貂都喜欢第一棵桉树。但是随着滴定程度的上升，食物中的桉树脑含量从0%到1%到2%到5% 到最终的10%，它们的行为开始出现变化。虽然不是完全像酸溶液完全被碱溶液中和时石蕊试剂突然从红变蓝那样迅速，但是也差不太多。

　　When the food was toxin-free, the possums spent an average of 40 minutes of every hour eating safely under treelike cover and only 20 minutes in the risky¹⁷, ground-like enclosure, and that scarcely changed for 1% and 2% cineole. The switch began at 5%, and by the time the cineole level had reached 10% the ratio of time the animals spent in the two enclosures had reversed itself—presumably reflecting, though this remains¹⁸ to be tested, the point at which they change trees in the wild.

　　当叶子无毒时，袋貂们每小时用平均40分钟的时间在树枝状的遮蔽物下安全的进食。而在危险的类地面的桉树上只待20分钟，这时的桉树脑含量变化在1%到2%之间。分界点出现在5%，当桉树脑含量达到10%，这些小动物们呆在这两颗桉树上的时间比完全颠倒过来了——这大致上能反映在野外环境下它们换树进食时的毒素量值，当然这还有待验证。

　　Though foxes are of recent introduction in Australia (having been brought for sport by British settlers), many marsupial¹⁹ predators, now extinct, were present before the arrival of man in both his Aboriginal²⁰ and his European forms, so the ecological system of plants, herbivores and carnivores in the eucalyptus forests would probably not have been that different in the evolutionary²¹ past. A neat illustration, then, of co-evolution between three different parts of an ecosystem—and of the value, even in biology, of precise measurement.

　　虽然狐狸是很晚才被引进到澳大利亚的（由英国移民出于狩猎运动的目的而带来的），但是在原始人或者欧洲人到来之前还有很多其他的有袋动物的猎食者（现在都灭绝了）。所以桉树林生态系统中的那些植物，素食动物肉食动物，与进化史中较早的生态系统相比，差别可能也没有那么大。这样一来生态系统中的三个不同角色的（植物，素食动物，肉食动物）协同进化的一张清晰的图表呈现出来。在生物学里也能进行精确的量化计算，这种尝试的价值是巨大的。

1 accusation   

n.控告，指责，谴责

参考例句：

• I was furious at his making such an accusation.我对他的这种责备非常气愤。
• She knew that no one would believe her accusation.她知道没人会相信她的指控。

2 spectrum   

n.谱，光谱，频谱；范围，幅度，系列

参考例句：

• This is a kind of atomic spectrum.这是一种原子光谱。
• We have known much of the constitution of the solar spectrum.关于太阳光谱的构成，我们已了解不少。

3 ecological   

adj.生态的，生态学的

参考例句：

• The region has been declared an ecological disaster zone.这个地区已经宣布为生态灾难区。
• Each animal has its ecological niche.每种动物都有自己的生态位.

4 dozed   

v.打盹儿，打瞌睡( doze的过去式和过去分词 )

参考例句：

• He boozed till daylight and dozed into the afternoon. 他喝了个通霄，昏沉沉地一直睡到下午。 来自《现代英汉综合大词典》
• I dozed off during the soporific music. 我听到这催人入睡的音乐，便不知不觉打起盹儿来了。 来自《简明英汉词典》

5 indicator   

n.指标；指示物，指示者；指示器

参考例句：

• Gold prices are often seen as an indicator of inflation.黃金价格常常被看作是通货膨胀的指标。
• His left-hand indicator is flashing.他左手边的转向灯正在闪亮。

6 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

7 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

8 eucalyptus   

n.桉树，桉属植物

参考例句：

• Eucalyptus oil is good for easing muscular aches and pains.桉树油可以很好地缓解肌肉的疼痛。
• The birds rustled in the eucalyptus trees.鸟在桉树弄出沙沙的响声。

9 browsed   

v.吃草( browse的过去式和过去分词 )；随意翻阅；（在商店里）随便看看；（在计算机上）浏览信息

参考例句：

• I browsed through some magazines while I waited. 我边等边浏览几本杂志。 来自辞典例句
• I browsed through the book, looking at page after page. 我翻开了一下全书，一页又一页。 来自互联网

10 toxins   

n.毒素( toxin的名词复数 )

参考例句：

• The seas have been used as a receptacle for a range of industrial toxins. 海洋成了各种有毒工业废料的大容器。
• Most toxins are naturally excreted from the body. 大部分毒素被自然排出体外。 来自《简明英汉词典》

11 toxic   

adj.有毒的，因中毒引起的

参考例句：

• The factory had accidentally released a quantity of toxic waste into the sea.这家工厂意外泄漏大量有毒废物到海中。
• There is a risk that toxic chemicals might be blasted into the atmosphere.爆炸后有毒化学物质可能会进入大气层。

12 mimicking   

v.（尤指为了逗乐而）模仿( mimic的现在分词 )；酷似

参考例句：

• She's always mimicking the teachers. 她总喜欢模仿老师的言谈举止。
• The boy made us all laugh by mimicking the teacher's voice. 这男孩模仿老师的声音，逗得我们大家都笑了。 来自辞典例句

13 arboreal   

adj.树栖的；树的

参考例句：

• Man was evolved from an ancestor that was probably arboreal.人大概是从住在树上的祖先进化而来的。
• Koala is an arboreal Australian marsupial.考拉是一种澳大利亚树栖有袋动物。

14 spiked   

adj.有穗的；成锥形的；有尖顶的

参考例句：

• The editor spiked the story. 编辑删去了这篇报道。 来自《简明英汉词典》
• They wondered whether their drinks had been spiked. 他们有些疑惑自己的饮料里是否被偷偷搀了烈性酒。 来自辞典例句

15 scent   

n.气味，香味，香水，线索，嗅觉；v.嗅，发觉

参考例句：

• The air was filled with the scent of lilac.空气中弥漫着丁香花的芬芳。
• The flowers give off a heady scent at night.这些花晚上散发出醉人的芳香。

16 scattered   

adj.分散的，稀疏的；散步的；疏疏落落的

参考例句：

• Gathering up his scattered papers,he pushed them into his case.他把散乱的文件收拾起来，塞进文件夹里。

17 risky   

adj.有风险的，冒险的

参考例句：

• It may be risky but we will chance it anyhow.这可能有危险，但我们无论如何要冒一冒险。
• He is well aware how risky this investment is.他心里对这项投资的风险十分清楚。

18 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

19 marsupial   

adj.有袋的，袋状的

参考例句：

• Koala is an arboreal Australian marsupial.考拉是一种澳大利亚树栖有袋动物。
• The marsupial has been in decline for decades due to urban sprawl from car accidentsdog attacks.这种有袋动物其数量在过去几十年间逐渐减少,主要原因是城市的扩张、车祸和狗的袭击。

20 aboriginal   

adj.（指动植物）土生的，原产地的，土著的

参考例句：

• They managed to wipe out the entire aboriginal population.他们终于把那些土著人全部消灭了。
• The lndians are the aboriginal Americans.印第安人是美国的土著人。

21 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。